Abstract: Multigrid algorithms based on the finite difference method of three dimensional（3D） convection diffusion equation are studied.The second order central difference and the fourth order compact difference schemes in general meth-size are presented.A partial semi-coarsening multigrid strategy is designed to solve the resulting sparse linear systems and the corresponding restriction and interpolation operators are also constructed.Finally，the computational results are compared with those computed by traditional multigrid method under full-coarsening strategy in equal mesh-size.The numerical experiments verify that the present partial semicoarsening multigrid method with general mesh-size is more accurate and efficient than the traditional multigrid method with equal mesh-size discretization for anisotropic problems.